Internal combustion engine

ABSTRACT

A piston ( 17 ) for an internal combustion engine. The piston ( 17 ) has a piston head ( 43 ) and a recess ( 46 ) formed in the piston head. A formation ( 91 ) is associated with the recess ( 46 ) for generating a turbulent motion in a fluid introduced into the recess. The formation ( 91 ) is configured to generate a swirling turbulent motion to the fluid introduced into the recess and preferably comprises spiral grooves ( 93 ) formed in the piston.

FIELD OF THE INVENTION

This invention relates to an internal combustion engine. Moreparticularly, the invention relates to a piston for a reciprocatinginternal combustion engine. The invention also relates to a controlsystem for a valve incorporated in a piston for an internal combustionengine

BACKGROUND ART

The invention has been devised particularly, although not exclusively,for an internal combustion engine of the type disclosed in U.S. Pat. No.5,261,358, the contents of which are incorporated herein by way ofreference.

With the abovementioned internal combustion engine, as also is the casewith most reciprocating piston internal combustion engines, it isparticularly desirable for fuel droplets to mix intimately with air inthe combustion chamber. One way in which this can be achieved is bysubjecting the air in the combustion chamber to a swirling motion.

With the abovementioned internal combustion engine, it is also desirablefor scavenging air introduced into the combustion chamber to undergoturbulent flow in order to perform an effective scavenging process.

Furthermore, in the abovementioned engine, the scavenging air isintroduced into the combustion chamber through a port in the pistonwhich is opened and closed by a valve. There is a need for a simple yeteffective system for controlling operation of the valve.

It is against this background that the present invention has beendeveloped.

DISCLOSURE OF THE INVENTION

According to one aspect of the present invention there is provided apiston for an internal combustion engine, the piston comprising a pistonhead, a recess formed in the piston head, and a formation associatedwith the recess for generating a turbulent motion in a fluid introducedinto the recess.

Preferably, the formation is configured to generate a swirling turbulentmotion to the fluid introduced into the recess.

The formation may comprise at least one spiral groove formed in thepiston. Preferably, there are a plurality of the spiral grooves disposedabout the recess. Conveniently, each of the spiral grooves extendsoutwardly from the recess and tapers inwardly in the direction in whichit spirals outwardly.

With this arrangement, combustion air contained in the combustionchamber is acted upon by the formation associated with the recess as thepiston performs a compression stroke, thereby causing the combustion airto undergo a turbulent motion which promotes mixing between the air andfuel droplets delivered into the combustion chamber.

In the case of an engine in which scavenging air is introduced into thecombustion chamber through a port in the head of the piston (as is thecase with the abovementioned engine disclosed in U.S. Pat. No.5,261,358), the formation may be arranged to impart a swirling motion tothe scavenging air entering the combustion chamber and so assist thescavenging process.

With this arrangement, the port through which the scavenging air isintroduced into the combustion chamber may open into the recess suchthat the incoming scavenging air is subjected to the influence of theformation.

The port may be opened and closed by a valve which is operable under theinfluence of a control system.

The control system may include a hydraulic lifter operable by ahydraulic fluid such as oil (which may, for example, be oil used forlubricating the engine). The control system may further include a fluidflow path along which hydraulic fluid is delivered to the hydrauliclifter, the fluid flow path including a first section and a secondsection. The second section is located in the piston and opens onto aside wall thereof. The first section is located in part of the enginewith respect to which the piston can reciprocate, and opens onto a sidewall of the cylinder in which the piston is housed. With thisarrangement, the second section registers with the first section for alimited period during reciprocation of the piston. When the piston isperforming an expansion stroke and there is registration between the twosections of the fluid flow path, hydraulic fluid flows from the firstsection to the second section thereby to cause operation of the valvelifter.

A bleed path may be associated with the second section to allowhydraulic fluid to bleed therefrom.

The control system may further include a spring means for biasing thevalve to a closed condition in relation to the port. Once the twosections of the fluid flow path have moved out of registration, theinfluence of the spring means causes the valve to return to the closedcondition, with hydraulic pressure on the valve lifter being relieved byfluid bleeding from the second section.

According to a second aspect of the invention, there is provided aninternal combustion engine having a piston according to the first aspectof the invention.

According to a third aspect of the invention there is provided a pistonfor an internal combustion engine, the piston comprising: a port formedin the head thereof through which a fluid can be delivered into acombustion chamber; a valve for opening and closing the port; and aformation in the piston head for imparting a swirling motion to fluiddelivered into the combustion chamber through the port upon openingthereof.

Preferably, the port is accommodated in a recess formed in the piston,the formation comprising a plurality of spiral grooves formed in thepiston about the recess.

The valve for opening and closing the port of the piston according tothe third aspect of the invention may be operable under the influence ofa control system as defined hereinbefore.

According to a fourth aspect of the invention, there is provided aninternal combustion engine having a piston according to the third aspectof the invention.

According to a fifth aspect of the invention there is provided a pistonfor an internal combustion engine, the piston comprising: a port formedin the head thereof through which a fluid can be delivered into acombustion chamber; a valve for opening and closing the port; and acontrol system for operating the valve, the control system including ahydraulic lifter operable by a hydraulic fluid such as oil (which may,for example, be oil used for lubricating the engine), the control systemfurther including a fluid flow path along which hydraulic fluid isdelivered to the hydraulic lifter, the fluid flow path having a firstsection and a second section, the second section being located in thepiston and opening onto a side wall thereof, and the first section beinglocated in part of the engine with respect to which the piston canreciprocate and opening onto a side wall of the cylinder in which thepiston is housed, whereby the second section can register with the firstsection for a limited period during reciprocation of the piston suchthat when the piston is performing a prescribed stroke and there isregistration between the two sections of the fluid flow path, hydraulicfluid can flow from the first section to the second section thereby tocause operation of the valve lifter.

According to sixth aspect of the invention, there is provided aninternal combustion engine having a piston according to the fifth aspectof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the followingdescription of one specific embodiment thereof, as shown in theaccompanying drawings in which:

FIG. 1 is a schematic sectional view of an engine according to theembodiment;

FIG. 2 is an end view of the engine of FIG. 1;

FIG. 3 is a schematic view of one cylinder of the engine shown in acondition in which it is undergoing a power stroke;

FIG. 4 is a view similar to FIG. 3 except that the cylinder is shown inan undergoing scavenging;

FIG. 5 is also a view similar to FIG. 3 with the exception that thecylinder is shown undergoing a compression stroke;

FIG. 6 is a schematic view of one of the pistons used in the engine;

FIG. 7 is a schematic view of a combustion chamber defined by one of thecylinders and the piston reciprocating within that cylinder;

FIG. 8 is a schematic view of the head end of the piston;

FIG. 9 is an end view of the piston shown in FIG. 8;

FIG. 10 is a schematic view of the piston in its cylinder;

FIG. 11 is a schematic view of the piston showing a scavenging valve andcontrol system therefore, the scavenging valve being shown in an opencondition;

FIG. 12 is a view similar to FIG. 11 with the exception that thescavenging valve is shown in a closed condition;

FIG. 13 is a further side view of the piston and cylinder, showing thepiston in a condition in which a fluid flow path is established forhydraulic fluid operating a hydraulic lifter which controls operation ofthe scavenging valve;

FIG. 14 is a view similar to FIG. 13 with the exception that the pistonis in a condition in which the fluid flow path is closed;

FIG. 15 is a schematic view of the piston showing part of the valvelifter and fluid flow path associated therewith;

FIG. 16 is a schematic side view of the piston showing a bleed path forhydraulic fluid when the fluid flow path is closed;

FIG. 17 is an end view of the engine showing the fluid flow pathdelivering hydraulic fluid to one cylinder of the engine; and

FIG. 18 is a view similar to FIG. 17 with the exception that the fluidflow path is shown delivering hydraulic fluid to another cylinder of theengine.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

The embodiment is directed to an internal combustion engine whichoperates in a similar fashion to the engine disclosed in U.S. Pat. No.5,261,352, the contents of which are incorporated herein by way ofreference.

The internal combustion engine comprises a housing 11 having a block 13and an oil sump 14. A plurality of cylinders 15 are defined within thehousing, there being four such cylinders in this embodiment. Eachcylinder 15 has a piston 17 reciprocating within it. Each piston 17 isoperatively connected to a drive shaft 19 by way of a swash plate 21.The piston 17 has a foot 23 received in a shoe 25 slidably supported onthe swash plate.

Each cylinder 15 is of stepped configuration so as to comprise twoportions, being a cylinder working portion 31 and a cylinder pumpingportion 32. The cylinder pumping portion 32 is of larger cross-sectionalarea than the cylinder working portion 31, as shown in the drawings. Thecylinder working portion 31 has a wall 33 at one of its ends, and thetwo cylinder portions open onto each other at the other end of thecylinder working portion. A transition wall 35 connects the two cylinderportions 31, 32 together at the location where they open onto eachother. The transition wall 35 provides the step in the cylinder 15.

The piston 17 is also of stepped configuration so as to comprise twoportions, being a piston working portion 41 and a piston pumping portion42. The piston working portion 41 is received within the cylinderworking portion 31, and the piston pumping portion 42 is received withinthe cylinder pumping portion 32. A transition portion 44 is providedbetween the piston working portion 41 and the piston pumping portion 42.

A combustion chamber 45 is defined by co-operation between the pistonworking portion 41 and the cylinder working portion 31.

The piston 17 has a head end 43 which confronts the combustion chamber45 and in which there is provided a recess 46 (the purpose of which willbe explained later).

An annular pumping chamber 47 is defined between the cylinder pumpingportion 32, the cylinder transition wall 35 and the piston 17.

The combustion chamber 45 and the pumping chamber 47 vary in volume asthe piston 17 undergoes reciprocation in the cylinder 15.

An inlet means 51 is provided to admit air into the pumping chamber 47as it undergoes an expansion in volume. The inlet means 51 includes aplurality of air inlet ports 53 which are provided in the cylindertransition wall 35 and which open onto the annular pumping chamber 47. Avalve (not shown) is associated with each inlet port 53 and is operableto permit air to flow through the port into the pumping chamber 47 uponexpansion of the pumping chamber while preventing return flow out of theport 53 upon volume reduction of the pumping chamber.

A transfer system 61 is provided for selectively transferring air fromthe pumping chamber 47 to the combustion chamber 45. The transfer system61 comprises a transfer chamber 63 within the piston 17 to receive airunder pressure from the pumping chamber 47 as the latter undergoes areduction in volume and to contain such air. The transfer chamber 63receives air from the pumping chamber 47 by way of a plurality oftransfer ports 65 provided in the transition portion 44 of the piston17. Each transfer port 65 opens onto the transfer chamber 63. A one-waytransfer valve 67 is provided in association with each transfer port 65and is operable to permit air to flow through the transfer port 65 intothe transfer chamber 63 upon volume reduction of the pumping chamber 47,while preventing return flow upon volume expansion of the pumpingchamber.

A valve system 71 is provided for controlling discharge of air from thetransfer chamber 63 to the combustion chamber 45. The valve system 71comprises a port 73 in the piston head 43, the port being located at thebase of the recess 46 and opening onto the recess. The valve system 71further comprises a discharge valve 75 for opening and closing thedischarge port 73.

The discharge valve 75 opens and closes under the control of a hydrauliccontrol system 77 which will be explained in more detail later. A springmeans 79 is provided for biasing the discharge valve 75 into theposition in which it closes the discharge port 73.

Air introduced into the combustion chamber 45 from the pumping chamber47 serves a scavenging function and may also be used for combustionpurposes. A combustible mixture which is introduced into the combustionchamber 45. A delivery system (not shown) including an inlet port whichis opened and closed in timed sequence by a valve may be provided fordelivery of combustion air into the combustion chamber, to supplementair delivered by way of the transfer system 61. A fuel injection system(not shown) may be provided for injecting fuel into the air to providethe combustible mixture. An exhaust system 81 is provided fordischarging products of combustion from the combustion chamber 45. Theexhaust system 81 includes an exhaust port 83 which is opened and closedin timed sequence by an exhaust valve 85.

The engine operates in a similar fashion to the engine disclosed in U.S.Pat. No. 5,261,358 and so will not be described in detail. The operationis, however, schematically illustrated in FIGS. 3, 4 and 5 of thedrawings. In FIG. 3 of the drawings, the piston 17 is shown performing apower stroke, with the result that the pumping chamber 47 undergoesexpansion to draw in air through inlet ports 53. As illustrated in FIG.4, towards the end of the power stroke, the discharge valve 75 and theexhaust valve 85 both open. This allows air under pressure within thetransfer chamber 63 to flow into the combustion chamber 45 and perform ascavenging process. FIG. 5 illustrates the subsequent compression strokewhere a combustible mixture in the combustion chamber 45 is compressed,and the volume reduction of the pumping chamber 47 causes air containedtherein to flow through the ports 65 into the transfer chamber 63.

As best seen in FIGS. 7, 8 and 9, a formation 91 is associated with therecess 46 for generating a turbulent motion in fluid within the recessand also in the combustion chamber 45. The formation 91 is in the formof a plurality of spiral grooves 93 formed in the head end 43 of thepiston 17. Each spiral groove 93 extends outwardly from the recess andtapers inwardly (i.e. narrows) in the direction in which it spiralsoutwardly.

With this arrangement, the scavenging air passing through the transferport 65 from the transfer chamber 63 to the combustion chamber 45 isinfluenced by the spiral grooves 93 so as to cause the scavenging air toundergo a turbulent motion. This turbulent motion assists in thescavenging process. Additionally, this turbulent motion subsequentlyassists in promoting mixing between the air and fuel droplets deliveredinto the combustion chamber to form the combustible mixture.Furthermore, the spiral grooves 93 generate a swirling motion in thecombustible mixture within the combustion chamber during the compressionprocess. This turbulent motion so generated further promotes mixingbetween the air and the fuel droplets.

As best seen in FIGS. 11 to 18, the hydraulic control system 77 for thedischarge valve 75 comprises a push rod 101 one end of which is formedintegrally with, or is connected to, the stem of the discharge valve 75,and the other end of which is connected to a control piston 103 receivedwithin a control cylinder 105. The control cylinder 105 is formed withinthe piston 17, as best seen in FIGS. 11 and 12 of the drawings. Acontrol chamber 107 is defined between the control piston 103 and thecontrol cylinder 105. The control chamber 107 is adapted to receivehydraulic fluid under pressure thereby to cause displacement of thecontrol piston 103 and corresponding displacement of the push rod 101which in turn moves the discharge valve 75 from the closed condition tothe open position, as shown in FIG. 11.

Hydraulic fluid is delivered to the chamber 107 via a plurality of flowpassages 109 defined by oil galleries formed in the piston 17. One endof each flow passage 109 communicates with the chamber 107 and the otherend of each flow passage communicates with a circumferential recess 111provided on the piston 17. The circumferential recess 111 is positionedon the outer surface of the piston pumping portion 43.

As the piston 17 reciprocates within the cylinder 15, thecircumferential recess 111 sequentially moves into and out ofregistration with a respective oil delivery port 115 in the side wall ofthe cylinder 15. The port 115 communicates with a flow passage. 117formed in the block 13. The flow passage 117 has an inlet region 119which sequentially communicates with an oil delivery circuit 121 formedin the drive shaft 19 of the engine. The oil delivery circuit 121includes an outlet port 123 which moves through a circular path withrotation of the drive shaft 19 and which sequentially communicates withthe flow passages 117 associated with the four cylinders, as best seenin FIGS. 17 and 18 of the drawings. In this way, oil is sequentiallydelivered from the delivery circuit 121 in the drive shaft 19 to each ofthe cylinders 15. The inlet regions 119 of the passages 117 are wide sothat there is minimal separation between adjacent passages 117 at theinlet regions 119 so as to allow smooth oil flow along the deliverycircuit 121 and thereby avoiding shock loading on the oil deliverysystem.

As the recess 111 of each piston 18 moves into registration with itsrespective oil delivery port 115, it receives oil under pressure whichcauses actuation of the discharge valve 75 in the manner previouslydescribed. Once the recess 111 has moved out of registration with thedelivery port, further oil flow is terminated. A bleed system 131 isprovided to allow oil under pressure to bleed from the control chamber107 so thereby allowing the discharge valve 75 to return to the closedcondition under the influence of the spring 79. The oil bled from thebleed system can return to the sump 14 of the engine.

From the foregoing it is evident that the engine according to theembodiment has a simple, yet highly effective, arrangement, foroperating the discharge valve 75 of each piston 17 in timed sequence.

It should be appreciated that the scope of the invention is not limitedto the scope of the embodiment described. In particular, it should beappreciated that a piston having a recess incorporating a spiralformation to assist in creation of swirling motion within a combustionchamber can be employed in engines other than of the type described andillustrated in the present embodiment.

Throughout the specification, unless the context requires otherwise, theword “comprise” or variations such as “comprises” or “comprising”, willbe understood to imply the inclusion of a stated integer or group ofintegers but not the exclusion of any other integer or group ofintegers.

The claims defining the invention are as follows:
 1. A piston for aninternal combustion engine, of the type having a combustion chamber, thepiston comprising a piston head, a recess formed in the piston head, aport communicating with the recess for delivery of a fluid into thecombustion chamber, and a formation associated with the recess forgenerating turbulent motion in the fluid delivered into the combustionchamber from the port through the recess.
 2. A piston according to claim1 wherein the formation is configured to generate a swirling turbulentmotion to the fluid.
 3. A piston according to claim 1 wherein theformation comprises at least one spiral groove formed in the piston. 4.A piston according to claim 3 wherein there are a plurality of thespiral grooves disposed about the recess.
 5. A piston according to claim4 wherein each of the spiral grooves extends outwardly from the recessand tapers inwardly in the direction in which it spirals outwardly.
 6. Apiston according to claim 1, wherein the formation is arranged andconfigured to impart a swirling motion to scavenging air entering thecombustion chamber through the port so as to assist the scavengingprocess.
 7. A piston according to claim 1, wherein the recess has a baseand the port is located at the base of the recess.
 8. A piston accordingto claim 6 wherein the port is opened and closed by a valve operableunder the influence of a control system.
 9. A piston according to claim8 wherein the control system comprises a hydraulic lifter operable by ahydraulic fluid.
 10. A piston according to claim 9 wherein the controlsystem further comprises a fluid flow path along which hydraulic fluidis delivered to the hydraulic lifter, the fluid flow path including afirst section and a second section.
 11. A piston according to claim 10wherein the second section is located in the piston and opens onto aside wall thereof.
 12. A piston according to claim 11 wherein the firstsection is located in part of the engine with respect to which thepiston can reciprocate, and opens onto a side wall of the cylinder inwhich the piston is housed.
 13. A piston according to claim 10 wherein ableed path is associated with the second section to allow hydraulicfluid to bleed therefrom.
 14. A piston according to claim 8 wherein thecontrol system further comprises a spring means for biasing the valve toa closed condition in relation to the port.
 15. A piston for an internalcombustion engine of the type having a combustion chamber, the pistoncomprising: a port formed in the head thereof through which a fluid canbe delivered into the combustion chamber; a valve for opening andclosing the port; and a formation in the piston head for imparting aswirling motion to fluid delivered into the combustion chamber throughthe port upon opening thereof.
 16. A piston according to claim 15wherein the port is accommodated in a recess formed in the piston, theformation comprising a plurality of spiral grooves formed in the pistonabout the recess.
 17. A piston according to claim 15 wherein the port isopened and closed by a valve operable under the influence of a controlsystem.
 18. A piston according to claim 17 wherein the control systemcomprises a hydraulic lifter operable by a hydraulic fluid.
 19. A pistonaccording to claim 18 wherein the control system further comprises afluid flow path along which hydraulic fluid is delivered to thehydraulic lifter, the fluid flow path including a first section and asecond section.
 20. A piston according to claim 19 wherein the secondsection is located in the piston and opens onto a side wall thereof. 21.A piston according to claim 20 wherein the first section is located inpart of the engine with respect to which the piston can reciprocate, andopens onto a side wall of the cylinder in which the piston is housed.22. A piston according to claim 19 wherein a bleed path is associatedwith the second section to allow hydraulic fluid to bleed therefrom. 23.A piston according to claim 18 wherein the control system furthercomprises a spring means for biasing the valve to a closed conditionrelation to the port.
 24. A piston for an internal combustion engine,the piston comprising: a port formed in the head thereof through which afluid can be delivered into a combustion chamber; a valve for openingand closing the port; and a control system for operating the valve, thecontrol system including a hydraulic lifter operable by a hydraulicfluid, the control system further including a fluid flow path alongwhich hydraulic fluid is delivered to the hydraulic lifter, the fluidflow path having a first section and a second section, the secondsection being located in the piston and opening onto a side wallthereof, and the first section being located in part of the engine withrespect to which the piston can reciprocate and opening onto a side wallof the cylinder in which the piston is housed, whereby the secondsection can register with the first section for a limited period duringreciprocation of the piston such that when the piston is performing aprescribed stroke and there is registration between the two sections ofthe fluid flow path, hydraulic fluid can flow from the first section tothe second section thereby to cause operation of the valve lifter.